LIVER FUNCTION Flashcards
Which of AST/ALT is generally the more sensitive test; and which is more liver-specific?
More sensitive= AST, but this is non-specific to liver. May also rise in muscle injury- rhabdomyolysis in one of the following organs: heart, skeletal muscle, kidneys, and pancreas
ALT is more liver specific but less sensitive.
How do you define ‘cholestasis’?
.An obstruction (e.g. gallstones) or drugs can cause blockage in the passage of bile from the gall bladder to the duodenum.
Symptoms include itchiness, jaundice, pale stools (implies obstructive cholestasis) and dark urine.
Early stages are detected by a rise in ALP and bile.
In later stages AST, ALT and bilirubin may be elevated.
Cholestasis is characterised by the accumulation of bile in liver cells and biliary passages.
In cholestasis, what LFT’s do we use to aid diagnosis? What if it is drug-induced cholestasis?
Use ALP in early stages
Drug-induced: ask for GGT
ONE of the functions of the liver is the metabolism/ handling of WHAT?
Drugs
Billirubin
Toxins e.g. ammonia
ONE of the functions of the liver is the synthesis of what?
Clotting factors Proteins Amino acids Cholesterol Bile
ONE of the functions of the liver is storage of what?
Ferritin
Glycogen
Vitamin K
Vitamins A, D, E
Paracetamol overdose can cause liver toxicity. What is the mechanism of this?
At normal doses, paracetamol is metabolised into the toxic metabolite NAPQI - this is then detoxified by conjugation with glutathione to form a non-toxic metabolite. In overdose, glutathione is exhausted and the toxic metabolite builds up causes liver damage.
Why can an increased INR value indicate liver damage? What about prothrombin time?
Due to less production of clotting factors- blood becomes thinner hence a higher INR
An Increased prothrombin time (clotting time) indicates liver impairment, increasing bleed risk
Does a high level of conjugated or unconjugated billirubin indicate liver damage?
UNCONJUGATED
In plasma, it is usually bound to albumin, and transported to the liver where it is conjugated by glucuronidation to form water soluble bilirubin. If the liver is damaged it can no longer do this, and bilirubin remains unconjugated.
NB: bilirubin is the yellow compound implicated in jaundice.
Liver disease may be caused by either liver cell destruction or cholestasis. What are some examples of liver cell destruction?
Alcohol, viral hepatitis, hepatotoxic drugs, cancer, autoimmune conditions or prolonged biliary obstruction
ALT/AST are liver enzymes (TRANSAMINASES) that when elevated indicate liver damage; these leak of of cells following liver cellular damage. Which of these is solely hepatic in origin and is therefore more liver specific?
ALT
We stop statins when liver transaminases are __x the upper limit of normal?
Stop statins if transaminases >3x upper limit.
When is the liver enzyme ALP (alkaline phosphatase) raised?
Raised in cholestasis, metastatic liver disease and with alcohol consumption.
What kind of liver disease may be present if there is a rise in both ALP and GGT?
An increase in both ALP and GGT is indicative of cholestasis.
When liver damage is due to alcohol, which increases more, ALT or AST? (we use this ratio to help
When liver damage is due to alcohol, AST often increases much more than ALT (this is a pattern seen with few other liver diseases). The classic ratio of AST/ALT >2 is seen in about 70% of cases.
